Hydraulic radially acting reciprocating engine



T. MULLER April 24, 1962 Filed June 12, 1961 HYDRAULIC RADIALLY ACTING RECIPROCATING ENGINE A 7 TORNEYS United States Patent 3,030,932 HYDRAULIC RADIALLY ACTING RECIPROCATING ENGINE Theodor Miiller, Winterthur, Switzerland, assignor to Schweizerische Lokomotivund Maschinenfabrik, Winterthur, Switzerland Filed June 12, 1961, Ser. No. 116,511 Claims priority, application Switzerland June 14, 1960 Claims. (Cl. 121-52) The present invention relates to hydraulic radially acting reciprocating engines which are operable as pump, motor or clutch, of the type in which the radial cylinder unit effects a circular rolling movement, caused by eccentric or other guiding members, relatively to the engine casing without rotating with respect to the latter, and the admission of fluid to the cylinders provided with ports is controlled by means of a rotary slide valve, and in which the free outer ends of the pistons provided with conical heads roll along guide paths displaced from the transverse middle plane during their to-and-fro movements in circumferential direction,

In radial piston engines of this type it is of advantage with respect to running technique that the pistons during their to-and-fro rolling movements along the eccentric guide paths can effect a rotary motion about their own axes. It is, however, disadvantageous that the track forces acting upon the piston heads, in cooperation with the fluid pressure acting upon the pistons from the interior, produce an axially directed force component during the pressure phase, which tends to tilt the cylinder unit and thus produce edge pressures on its bearings. When in addition the casing and the cylinder unit are rotatably arranged, this undesirable effect even increases owing to the centrifugal forces acting upon the pistons.

It is an object of the present invention to substantially prevent these disadvantageous effects and even to completely avoid them with a suitable arrangement and dimensioning of the structural parts. According to the invention the engine casing is provided with a guide path for the pistons on either side of the transverse middle plane of the piston and cylinder unit assembly, and each piston comprises two coaxial parts including a core plunger movable within a sleeve plunger, the outer end of the sleeve plunger coacting with one of said guide paths and the outer end of the core plunger coacting with the other guide path. It is possible to arrange and distribute the surfaces of the plungers subjected to the pressure of the operating fluid, and to select the abutting points of the plunger heads on the casing in such a manner that the axial forces acting on the individual plunger members of the pistons will compensate each other completely and the cylinder walls will not be subjected to axial pressures.

The present invention will now be described in more detail with reference to the accompanying drawings in which:

FIGURE 1 is an axial section through a preferred embodiment of a piston engine according to the invention, operating as a pump, on the line 1-1 of FIGURE 2,

FIGURE 2 is a transverse section through the pump according to the line 11-11 of FIGURE 1, and

FIGURE 3 is a longitudinal section through a cylinder drawn to a larger scale and indicating the forces arising during operation.

The two-part engine casing 1 carries two bearings 2 for the drive shaft 3. A cylinder unit 5 comprising six cylinders 7 is rotatably supported upon the crank 4 of the shaft 3 by the intermediary of a control sleeve 6. The sleeve 6 is provided with a port 8 for each of the cylinders 7. Owing to the rotary movement of the crank 4 the cylinder unit 5 carries out a circular rolling movement within the casing 1 and is guided by the two auxiliary cranks 9 without rotation with respect to the casing. Ducts 10 and 11 are provided in the shaft 3 for the sup ply and the discharge of operating fluid to and from the crank 4. These ducts open into the suction slot 12 and the delivery slot 13, respectively, in the crank. While one half of the number of cylinders 7 is connected by openings 8 to the suction slot 12, the other one-half of the number of cylinders is connected to the delivery slot 13 located at the opposite side of the crank 4. It is assumed that the drive shaft 3 rotates in counter-clockwise rotation (arrow W).

The pistons reciprocating in the cylinders consist each of two parts; a core plunger 14 and a sleeve plunger 15 are arranged within the cylinders 7. As seen in FIG. 3, the sleeve plunger 15 is provided with a conical head rim 16 abutting against the left-hand eccentric guiding path 17 of the plate 18 inserted in the casing 1. The core plunger 14 is mounted within the sleeve plunger 15 for longitudinal movement relatively thereto, and the conical head 1a of plunger 14 is urged by fluid pressure against the righthand eccentric guiding path 20 of plates 18. The two guiding paths are arranged in rooflike manner with respect to the middle transverse plane through the piston assembly.

A disk 21 mounted on the sleeve plunger 15 and a counter-guiding path 22 provided on the casing I serve to prevent the pistons from moving too far away from the respective guide paths, while the core plunger 14 is protected by its own head 19, projecting beyond the head of the sleeve plunger 15, against sliding back into the sleeve plunger 15.

As shown in FIG. 3, the sleeve pressure is subjected to the fluid pressure P and the abutting pressure P =P cos a At the point of intersection of these forces, they can be composed to the resulting axial force P igot This axial force is counteracted by the forces P and P =P /c0s oz; acting on the plunger 14, the resultant of said forces being equal to P .tga also acting upon the sleeve plunger. When selecting the sectional ratio of the two plunger members, the points of application of the forces P' P and also the inclinations of the guide path surfaces with respect to the transverse middle plane through the piston assembly are so that the axial forces P iga and P .tgoc are acting at the same point of the cylinder axis and are of equal magnitude, these axial forces then neutralize each other completely and no axial force thus acts from the sleeve plunger 15 upon the cylinder wall. As pointed out this balance of forces is obtained when the condition P Jga =P JgOc is satisfied. This is possible, in spite of the fact that tgoc is not equal to tga when the proportion between the cross-sectional area of the sleeve plunger 15 and the cross-sectional area of the core plunger 14 is equal to the proportion of Iga /lgoc Instead of arranging the shaft 3 to rotate as in the embodiment described, the casing and the cylinder unit could be made to rotate while the shaft remains stationary. When the machine shall operate as shaft coupling, provision must be made for closing the delivery conduit by any closure means, since otherwise the machine could transmit any torque.

Also the weight of the plungers can be adjusted so that with a rotatably arranged cylinder unit, the axial forces produced due to the centrifugal forces of the plungers will compensate each other completely.

It is evident that the invention can also be applied to radial piston engines, in which the eccentricity of the crank 4 can be adjusted and the auxiliary cranks 9 thus will be replaced by adjustable guide members. However, since the type of construction of these members is without importance for the practice of the present invention, the illustration and description of such members is omitted.

I claim:

1. A hydraulic radially acting reciprocating engine comprising a casing, a radial cylinder unit mounted eccentrically within the casing for effecting a circular rolling movement without relative rotation with respect to the casing, rotary valve means for controlling admission and delivery of fluid to and from the cylinders, a two-part plunger piston reciprocating in each cylinder, each plunger piston including a pair of coaxially arranged core and sleeve plungers movable one within the other, guide paths for the outer ends of said plungers provided on said casing, each pair of plungers coacting with two guide paths disposed each at one side of the transverse middle plane of the cylinder unit, said core plunger coacting with one guide path and said sleeve plunger coacting withthe other guide path.

2. A radially acting reciprocating engine according to claim 1, wherein the head of the core plunger projects outwardly beyond the head of the sleeve plunger.

3. A radially acting reciprocating engine according to claim 2, wherein the heads of the two plungers are conical and the two guide paths are rooflike oppositely inclined surfaces.

4. A radially acting reciprocating engine according to claim 3, wherein the cross-sectional ratio of the two plungers and the inclination of the guiding surfaces with respect to said transverse middle plane is selected so that the resultant of all forces, acting upon the plungers during operation and due to the pressure medium, the guide paths and the dynamic forces, does not have any axially directed component.

5. A radially acting reciprocating engine according to claim 1, wherein the casing is provided with a counterguiding path for the sleeve plunger in order to prevent separation of the plunger heads from the guide paths, while the head of the core plunger coacts with the sleeve plunger to prevent the core plunger from sliding back into the sleeve plunger.

Graf von Soden Jan. 10, 1961 3,010,405 Tomell Nov. 28, 1961 

